Motors that can be driven slowly with 5volts

I'm designing a solar tracking module and i need to knwo which motor would allow me to slowly move a solar panel,and tilt it towards the sun's insolation.
Ideally i would have used a linear actuator but it needs 230V mains and also very expensive
So which motor is would suit this application,and also not too expensive DC,Servo or stepper motors.I dont wanna have to use gears to reduce the speed of the motor

You are going to need gearing just for strength against the wind (like Panic Mode said).

Just buy a cheap "DC gearmotor" from ebay or one of the hobby robot suppliers. These have gearing already built into the end of the motor, you can easily get 100:1 gearing, and a 12v motor will still work ok on 5v although it will be slower (which is what you want).